#include<iostream>
#include<map>
#include<vector>

using namespace std;
int main(){

	freopen("input.txt","r",stdin);
	string s,s1;
	cin>>s>>s1;
	int i=0,j=0;
	map<char,int> m;
	vector<char> v;
	while(i<s.length()||j<s1.length()){
		// cout<<i<<" "<<j<<" "<<s[i]<<" "<<s1[j]<<endl;
		if(s[i]!=s1[j]){
			if(s[i]>='a'&&s[i]<='z'){
				if(m[s[i]-32]==0) v.push_back(s[i]-32);
				m[s[i]-32]++;
				
			}else{
				if(m[s[i]]==0) v.push_back(s[i]);
				m[s[i]]++;
			}
			i++;
		}else{
			i++;
			j++;
		}
	}

	for(auto i:v){
		cout<<i;
	}
}